Sealing line adjustable sealing device

ABSTRACT

A sealing device forms a sealing line on a package film enclosing an article with the package film being properly tensioned. The sealing device includes two conveyor belts for conveying the article and the package film in a forward direction. The conveyor belts are spaced from each other in the forward direction, defining a gap therebetween. A movable carrier plate carries and supports upper and lower sealing members with the conveyor belts arranged between the upper and lower members. The upper and lower members, to which heat sealing blades are attached, are moveable with respect to each other through the gap between the conveyor belts for bringing heat sealing blade to engage the package film, and thus forming a sealing line on the package film. A stationary bottom plate is arranged below the carrier plate and supports a plurality of guide rods movably engaging the carrier plate for guiding the movement of the carrier plate with respect to the conveyor belts. A motor is mounted on the bottom plate and is coupled to a worm-gear based speed reduction system. The worm, serving as an output shaft, threadingly and thus drivingly engages the carrier plate for moving the carrier plate along the guide rods thereby repositioning the upper and lower members with respect to the conveyor belts thereby changing relative position of the upper and lower member with respect to the article carried by the conveyor belts for adjusting the position of the sealing line.

FIELD OF THE INVENTION

[0001] The present invention generally relates to a sealing device for forming a sealing line on a package film enclosing an article and thus packaging the article, and in particular to a sealing device capable to adjust the position of the sealing line with respect to the article and control tensioning of the package film for obtaining an excellent sealing result.

BACKGROUND OF THE INVENTION

[0002] Package films made of plastics or other heat sealable materials are widely used in packaging a variety of products, such as foods, compact disks for computer software and music and books, to protect the products from being damaged or contaminated. In a packaging process, a package film is placed around an article to be packaged. Edges of the package film is then heated to seal together along a leading side, a tailing side and lateral sides of the article with the film tensioned to tightly enclose the article. To be more appealing to the general consumers, the package film must tightly enclose the article and sealed along sides of the article by properly formed sealing lines. As a general aesthetic requirement, a sealing line is desiredly formed at a position substantially bisecting thickness of the article.

[0003] A conventional sealing machine forms an L-shaped sealing line along two adjacent sides of an article to be packaged. Movable members carrying heat-sealing blades are allowed to move to each other for engaging and thus forming a sealing line on the package film enclosing an article. The article to be packaged is usually positioned on a platform or carried by a conveyor belt when the sealing operation is performed. However, the position where the heat-sealing blades engage the package film is fixed with respect to the platform or the conveyor belt whereby the position of the sealing line formed by the conventional sealing device is fixed with respect to the platform or the conveyor belt regardless the difference in thickness of different articles. This causes deficiency of the final package.

[0004] For example, as shown in FIG. 8 of the attached drawings, in packaging an article A having a small thickness, a sealing line B is formed at a position above a middle line of the thickness of the article A. Under this situation, the package film may be under-tensioned forming a loose package. This causes a waste of the package film.

[0005] On the other hand, as shown in FIG. 9 of the attached drawings, in packaging an article A′ having a large thickness, a sealing line B′ is formed at a position below the middle line of the thickness of the article A′. The package film may be over-tensioned and wrapping around the article with excessive tightness, causing damage to the package film and the article to be packaged.

SUMMARY OF THE INVENTION

[0006] Accordingly, an object of the present invention is to provide a sealing device that is capable to adjust the position of the sealing line formed thereby on an article for accommodation of articles of different thickness.

[0007] Another object of the present invention is to provide a sealing device for enclosing an article with a package film with the package film being properly tensioned.

[0008] A further object of the present invention is to provide a sealing device which causes no waste of the package film due to under-tensioning of the package film.

[0009] A still further object of the present invention is to provide a sealing device which causes no damage to the package film and the article to be packaged by over-tensioning the package film.

[0010] To achieve the above objects, in accordance with the present invention, there is provided a sealing device comprising two conveyor belts for conveying an article and a package film surrounding the article in a forward direction. The conveyor belts are spaced from each other in the forward direction, defining a gap therebetween. A movable carrier plate carries and supports upper and lower sealing members with the conveyor belts arranged between the upper and lower members. The upper and lower members, to which heat sealing blades are attached, are moveable with respect to each other through the gap between the conveyor belts for bringing heat sealing blade to engage the package film, and thus forming a sealing line on the package film. A stationary bottom plate is arranged below the carrier plate and supports a plurality of guide rods movably engaging the carrier plate for guiding the movement of the carrier plate with respect to the conveyor belts. A motor is mounted on the bottom plate and is coupled to a worm-gear based speed reduction system. The worm, serving as an output shaft, threadingly and thus drivingly engages the carrier plate for moving the carrier plate along the guide rods thereby repositioning the upper and lower members with respect to the conveyor belts thereby changing relative position of the upper and lower member with respect to the article carried by the conveyor belts for adjusting the position of the sealing line and controlling tensioning of the package film.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will be apparent to those skilled in the art by reading the following description of a preferred embodiment thereof, with reference to the attached drawings, in which:

[0012]FIG. 1 is a perspective view of a sealing device constructed in accordance with the present invention;

[0013]FIG. 2 is a side elevational view of the sealing device of the present invention;

[0014]FIG. 3 is a perspective view of an elevating system of the sealing device of the present invention;

[0015]FIG. 4 is a top plan view of the elevating system of the present invention;

[0016]FIG. 5 is a side elevational view of the elevating system of the present invention;

[0017]FIG. 6 is a side elevational view showing the sealing device of the present invention performing a sealing operation on an article having a small thickness;

[0018]FIG. 7 is similar to FIG. 6 but showing the sealing device of the present invention performing a sealing operation on an article having a large thickness;

[0019]FIGS. 8 and 9 are schematic views showing sealing lines formed by a conventional sealing device on articles having small and large thickness.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0020] With reference to the drawings and in particular to FIGS. 1 and 2, a sealing line adjustable sealing device constructed in accordance with the present invention, generally designated with reference numeral 100, comprises a movable carrier plate 10 on which heat-sealing means 20 is mounted. The heat-sealing means 20 comprises upper and lower members 21, 22 sized and positioned in correspondence to each other. Heat-sealing blades 23 are attached to the upper and lower members. The upper and lower members 21, 22 are movable with respect to each other to bring the heat sealing blades 23 to engage and perform heat-sealing operation on a package film (not labeled) enclosing an article C, C′ (see FIGS. 6 and 7). In the embodiment illustrated, two heat-sealing blades 23 are mounted to each of the upper and lower members 21, 22 along a front edge and one lateral edge of the member 21, 22. It is however, possible to mount more or less heat-sealing blades 23 to the upper and lower members 21, 22 and the heat-sealing blades 23 can be arranged in any desired configuration.

[0021] Two spaced conveyor belts 30, 40 are arranged between the upper and lower members 21, 22 in a direction to forward the article through the sealing device 100. A gap X is present between the conveyor belts 30, 40. The gap X is sized to allow the upper or lower member 21, 22 to move therethrough for engaging the package film.

[0022] Also referring to FIGS. 3-5, the sealing device 100 comprises an elevating means 50 located below the carrier plate 10. The elevating means 50 comprises a stationary bottom plate 51 which is rectangular in the embodiment illustrated. Four guide posts 52 are mounted to and extend upward from comers of the bottom plate 51. The guide posts 52 extend through corresponding bores (not labeled) defined in the carrier plate 10 for guiding movement of the carrier plate 10. A driving device 53 is mounted on the bottom plate 51 and is mechanically coupled to a speed reduction system which in the embodiment illustrated comprises two speed reduction devices 54. An illustrative example of the driving device 53 is an electrical motor. The speed reduction devices 54 are worm-gear based speed reduction devices.

[0023] The driving device 53 has an output spindle 531 on which a gear 532 is mounted. Each speed reduction device 54 comprises a horizontally-extending input shaft 541 and a vertically-extending worm 542 which is driven by the input shaft 541. A gear 543 is mounted to the input shaft 541 of the first speed reduction device 54 and is mechanically coupled to the gear 532 of the driving device 53 by a chain or timing belt 55. An additional gear 543 is mounted to the input shaft 541 of the first speed reduction device 54 and is coupled to a gear 543 that is mounted to the input shaft 541 of the second speed reduction device 54 by a chain or timing belt 56 for simultaneously driving the second speed reduction device 54. Although gear-chain systems are used to mechanically couple the speed reduction devices 54 to the driving device 53, it it apparent that other mechanical transmission systems may be employed to replace the gear-chain systems.

[0024] Connection members 57 defining inner-threaded bores (not shown) are mounted to the carrier plate 10 for threadingly engaging the worms 542 whereby when the worms 542 are rotated by the driving device 53, the carrier plate 10 is moved upward and/or downward thereby moving and re-positioning the heat-sealing means 20 with respect to the article C, C′ for adjusting the position of a sealing line formed on the package film.

[0025] The elevating means 50 comprises upper and lower limit sensors 58, 59, arranged above and below the carrier plate 10 for limiting the upward and downward movement of the carrier plate 10. When the carrier plate 10 is detected by the sensors 58, 59, the driving device 53 may be temporarily shut down or the driving device 53 may be operated in a reverse direction. Electrical circuits may be incorporated to control the operation of the driving device 53 or the movement of the carrier plate 10. The circuits, however, are well known and thus no further detail will be needed.

[0026] Also referring to FIGS. 6 and 7, the vertical position of the carrier plate 10 with respect to the article C, C′ to be packaged can be adjusted by operating the elevating means 50 for accommodating articles of different thickness. As shown in FIG. 6, in the case of an article C having a small thickness (FIG. 6), the sealing line E formed by a conventional sealing device is in general located above a middle line that bisects the thickness of the article C. By adjusting (raising) the vertical position of the carrier plate 10 in accordance with the present invention, the upper and lower members 21, 22 of the heat-sealing means 20 are re-positioned corresponding to the middle line of the article C and the sealing line E is substantially corresponding to the middle line of the article C. In the case of an article C′ having a large thickness (FIG. 7), the sealing line E′ formed by the conventional sealing device is in general below the middle line of the article C′. Similarly, this problem can be overcome by adjusting (lowering) the vertical position of the carrier plate 10 in accordance with the present invention whereby the sealing line E′ is located at a position substantially corresponding to the middle line of the article C′. .

[0027] In the embodiment illustrated, the movement of the carrier plate 10 is realized by the operation of the driving device 53. The operation of the driving device 53 can be controlled by a micro-processor based control system (not shown). Alternatively, the repositioning of the carrier plate 10 can be monitored visually and/or controlled manually.

[0028] Although the present invention has been described with reference to the preferred embodiment thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims. For example, the gear-chain system that couples the speed reduction devices to the driving device can be replaced by a pulley-belt system. 

What is claimed is
 1. A sealing device adapted to form a sealing line on a package film enclosing an article, the sealing device comprising: a conveyor system adapted to convey the article and the package film; a sealing system comprising a movable carrier plate on which upper and lower sealing members are mounted with the conveyor system arranged between the upper and lower members, the upper and lower members being moveable with respect to each other for engaging and forming a sealing line on the package film; and an elevating means comprising: a plurality of guide rods extending in a predetermined direction and movably engaging the carrier plate for guiding the movement of the carrier plate in the predetermined direction with respect to the conveyor system, and a carrier moving system comprising a driving device and at least a toothed output shaft driven by the driving device and drivingly engaging the carrier plate for moving the carrier plate along the guide rods thereby re-positioning the sealing system with respect to the conveyor system and the article.
 2. The sealing device as claimed in claim 1, wherein the conveyor system comprises first and second conveyor belts spaced from each other, defining a gap therebetween through which the upper and lower sealing members move with respect to each other.
 3. The sealing device as claimed in claim 1, wherein each sealing member has a front edge and a lateral edge to each of which a heat-sealing blade is attached.
 4. The sealing device as claimed in claim 1, wherein the elevating means comprises a bottom plate on which the driving device and the toothed output shaft are mounted.
 5. The sealing device as claimed in claim 1, wherein the driving device comprises a motor.
 6. The sealing device as claimed in claim 1, wherein the driving device has an output spindle which is mechanically coupled to the toothed output shaft by a speed reduction system.
 7. The sealing device as claimed in claim 6, wherein the speed reduction system comprises a worm-gear speed reduction device comprising a worm on which the toothed output shaft is formed, the speed reduction device having an input shaft with a first gear mounted therein, a second gear being mounted to the spindle of the driving device and coupled to the first gear by a chain for driving the speed reduction system.
 8. The sealing device as claimed in claim 6, wherein the speed reduction system comprises two worm-gear based speed reduction devices mechanically coupled to each other for simultaneous operation.
 9. The sealing device as claimed in claim 8, wherein each speed reduction device has an input shaft with a gear mounted thereon, the gears being coupled together by a chain.
 10. The sealing device as claimed in claim 1, wherein the carrier plate comprises a threaded coupling member threadingly engaging the toothed output shaft of the carrier moving system for moving the carrier plate.
 11. The sealing device as claimed in claim 1, wherein the elevating means comprises upper and lower limit sensors arranged above and below the carrier plate for limiting upward and downward movement of the carrier plate. 